BEIRUT — Syrian rebels captured a military base in the south on Wednesday and set their sights on seizing control of a strategically important region along the border with Jordan that would give them a critical gateway to attempt an attack on the capital, Damascus.
With foreign aid and training of rebels in Jordan ramping up, the opposition fighters have regained momentum in their fight to topple President Bashar Assad.
But while the fall of southern Syria would facilitate the rebel push for Damascus, it might also create dangerous complications, potentially drawing Syria’s neighbors into the two-year-old civil war. Besides abutting Jordan, the region borders Syria’s side of the Golan Heights, along a sensitive frontier with Israel.
‘‘This is a very sensitive triangle we are talking about,’’ said Hisham Jaber, a retired Lebanese Army general who heads the Middle East Center for Studies and Political Research in Beirut. ‘‘The fall of Daraa, if it happens, may usher in strategic changes in the area.’’
For the rebels, control of the south is key to their advance toward Damascus.
Dozens of fighting brigades have carved out footholds in areas to the east and south of the capital, where they fire off mortar shells on the heavily guarded city.
The significance of their gains in the south was on display Wednesday when the rebels stormed a military base after a five-day siege.
‘‘Damascus will be liberated from here, from Daraa, from the south,’’ declared an armed fighter, a rifle slung over his shoulder and a kaffiyeh tied around his face. Videos posted online by activists showed him and other unidentified rebels celebrating inside the Syrian Army’s 49th battalion in the village of Alma, on the outskirts of Daraa.
The videos showed rebels from the Suqour Houran, or Eagles of Houran brigade, driving a Russian-made armored personnel carrier inside the base. ‘‘These missiles are now under our control,’’ said a fighter, standing before a missile loaded on a truck.
The capture of the base is the latest advance by opposition fighters near the strategic border with Jordan. Last month, opposition fighters seized Dael, one of the province’s bigger towns, and overran another air defense base in the region.
Opposition fighters battling Assad’s troops have been chipping away at the regime’s hold on the southern part of the country in recent weeks with the help of an influx of foreign-funded weapons.
Their aim is to secure a corridor from the Jordanian border to Damascus in preparation for an eventual assault on the capital. And they have made major progress along the way. Activists say several towns and villages along the Daraa-Damascus route are now in rebel hands.
A Western diplomat who monitors Syria from his base in Jordan said the fall of Daraa appeared imminent, possibly in the next few days or weeks. His assessment was based on classified intelligence information, he said.
Daraa’s fall could unleash lawlessness on Jordan’s northern border and send jitters across the kingdom, a key US ally which fears Islamic extremist groups on its doorstep.
Also of grave concern are rebel advances in areas near the Israeli-occupied Golan Heights.
‘‘If Daraa falls, the rebels will come face-to-face with the Israeli army in the Golan,’’ said Hilal Khashan, a political science professor at the American University of Beirut.